Enbridge reports 81-foot segment of Line 5 is now unsupported by Straits floor due to erosion

In 2013, the National Wildlife Federation sent divers to look at Enbridge, Inc.'s aging straits pipelines, finding wide spans of unsupported structures encrusted with exotic zebra mussels and quagga mussels.

Canadian oil giant Enbridge reported an 81-foot segment of its Line 5 is now unsupported by the bottom of the Straits of Mackinac — more than the 75-foot limit stated in its easement agreement with the state of Michigan.

Due to the strong currents in the Straits of Mackinac, which oscillate between Lakes Huron and Michigan, the sands on the bottom of them are known to drastically shift, at times requiring Enbridge to add more anchors. It's part of the reason why an increasing chorus of environmentalists have grown concerned with the aging pipeline, with experts warning that an oil spill could potentially flow into both lakes.

Per the easement agreement, the company has 90 days to anchor unsupported spans. According to a statement, the company reported the span on Wednesday, and is awaiting approval from the Army Corps of Engineers to install the new anchors. The company says it can install the anchors in two days, weather permitting.

"Enbridge is reporting the span length on this one span because it believes its agreement with the State is valid," a statement from the company says. "We remain in compliance with the easement. We have already filed permit applications to do the work to address the spans and have received the state permits from EGLE."

"The current span length poses no integrity or safety risk to the pipeline," the statement adds.

The 66-year-old oil and gas pipeline has come under increasing scrutiny in recent years. In 2017, Enbridge downplayed the fact that a coating covering the pipeline had eroded. And last year, it was revealed that an anchor from a vessel struck the pipeline, damaging the pipeline with three small dents. Additionally, the pipes have become encrusted with invasive zebra and quagga mussels.

Attorney General Dana Nessel filed a lawsuit earlier this summer seeking to shut the pipeline down. Meanwhile, Gov. Gretchen Whitmer has asked the Michigan Department of Natural Resources to issue an opinion on whether Enbridge is in compliance with the original 1953 easement agreement with the state.

Stay on top of Detroit news and views. Sign up for our weekly issue newsletter delivered each Wednesday.